blog210904. Eclipse之EclipseContext的lazy compute, 延迟计算

• Lazy compute
• IContextFunction
• Lazy compute的实现

本文以eclipse 4.20为参考.

Lazy compute

EclipseContext实现了IEclipseContext接口. 其主要的作用是将application与container隔离开来.
其基本使用方法是container将值set写入EclipseContext, application读取get使用, 或反之. 也就是大致等同于一个map.
EclipseContext中一个明显的增强是lazy compute.
即允许set写入EclipseContext的值是一个compute(实则是一个function), 而当get读取时, 再执行这个compute, 取其结果.这样的实际效果就是lazy compute.

IContextFunction

描述上述compute的是IContextFunction

public interface IContextFunction  {
	//..........
	Object compute(IEclipseContext context, String contextKey);
	//..........
}

典型的用法,

public class WorkbenchPlugin extends AbstractUIPlugin {
	//... ... 
	public void initializeContext(IEclipseContext context) {
		e4Context = context;
		//... ... 
		context.set(IEditorRegistry.class.getName(), new ContextFunction() {
			@Override
			public Object compute(IEclipseContext context, String contextKey) {
				if (editorRegistry == null) {
					editorRegistry = new EditorRegistry(Platform.getContentTypeManager());
				}
				return editorRegistry;
			}
		});
		//... ... 		
	}
	//... ... 
}

Lazy compute的实现

参与lazy compute的类包括

• EclipseContext
• ValueComputation

EclipseContext.set()时, 直接保存IContextFunction instance.
当EclipseContext.get()时, 封装该instance到ValueComputation中, 并运行IContextFunction.compute()计算结果, 返回.
至此完成整个lazy compute过程.

驽马一架 2021/9/4